probably sand and reseal the floor.

Wipe the floor with a damp rag. That should indicate the colour it will be when you seal it. If the colour looks OK then simply sand the small area and seal it with some of the same finish that is on the floor now.

Thanks for your help: I had these floors refinished professionally 10 years ago when I bought the house. They used a water based finish. I don't think the people I used are in business any longer, and to be honest, I cannot afford to have the entire floor refinished right now (it's a small home with wood floors in every room). The hallway connects the living room and the kitchen. This spot is in the hallway, going into the kitchen. Part of the spot has lightened up, the rest of it still feels a bit damp. The stain is many shades darker than the floor. I don't know how much more it will lighten up.
I have never done anything before with my floors, so I am not sure what technique to use or where to buy what I need. Can anyone give me specific information about how to do this. I am pretty good at doing tedious things, and am a careful worker. I am also pretty broke right now so I would rather do this myself than have to hire someone in to take care of it.
Thanks

The floor finish (sheen) is one thing, the floor color is another. Are the floors finished identically in a closet or other hidden area? If a hidden place is available, similar damage could be done there deliberately so that repair methods could be tested. Nothing in the original post indicates previous experience with problems like this. Previous experience would help a bunch. But liquid shoe polish might get the color back in the ballpark. Too light at first is OK, more can be added later. Testing in a hidden area is best.

Well, when I had the floors refinished, I liked the light oak color, so I did not have them stain the floors. They just put the water based sealer on the floors. I think 3 coats. What has happened is that the cleaner that leaked onto the floor has left a dribbly almost coffee colored stain. And then there is a ring from where the bottom of the cleaner container stood on the floor. I realize now there must be a small leak in the bottom of the spray bottle as it was wet when i picked it up. I kind if scratched away at the stain with my nail and can pick up a bit of what I guess is the sealer. It's still a bit tacky right now. It's been raining here, so it hasn't really had time to dry out completely. I am guessing I should wait until this dries out completely before doing anything?
Answering your question about if there is an area I can test it out: Two of the rooms on the same floor have carpet on them, and I did not bother refinishing them since I knew I was going to put carpet on top of the floors. There actually is no hall closet or anyplace I could try duplicating the stain, is what I am trying to say.
YIPES! I am so mad at myself!

If the finish is still there then the damage may only be to the finish. Go to your local paint store and pick up a quart or pint of water based floor finsh. Get the proper sheen to match your floor. It comes in gloss or satin finish.
Get some sand paper and sand the stained area lightly until the mark is gone. Then apply some finish. Sand lightly (120 grit) to get the roughness off, between coats and apply three coats.

I'm not sure if you need it to dry out or not...but if you do, putting a dehumidifier in that room will help. We just had floor damage from a water leak, and my hardwood floor guy first made me put a consumer dehumidifier in the room, then had us rent an industrial dehumidifier. For the small area you're working with, a small dehumidifier would probably work well. It'll get rid of the dampness. You'll be lucky if just the clearcoat was affected, because you should be able to spot treat that and it'll be fine. If this cleaner absorbed deep into the wood, it's possible that even hard sanding won't work because you'll be taking too much wood off---might need to replace floor boards in that case.