Carol - you have a couple of options -

call a mason / cement contractor to have the opening sealed.

Call a window contractor to have the window replaced.

I believe both types of contractors will fix the issue temporarily until they can get to the job and provide a permanent solution.

They make vinyl with glass windows for basement applications which would continue to give you a bit of natural light in the basement but wouldn't rot out again.

Thanks for the advice. I will check out the price of a mason vs a vinyl window replacement. Right now I have a roof tarp and dry wall (green board) pieces over the open window, not pretty, safe or a good solution.

+1

If you are going to just close it up, call a mason. If you want to stick glass in it, look for an inorganic medium (i.e. not wood) with glass.