If the battery was going to go "boom" (or catch fire ), it would have done so by now. Once you get the plane down you need to carefully inspect the battery for any bulging. If no bulging is visable, then go ahead and charge it, BUT KEEP A VERY CLOSE EYE ON IT WHILE IT IS CHARGING.

You will definitely want to do this battery charge outside. Have a bucket of salted water near the charging area, and if you see any bulging at all, disconnect the battery and drop it in the bucket of salted water.