M.K.
My daughter went through this as well and in a couple of days he should figure out how to get himself down. I tried to speed up the process by "teaching" her how to fall down onto her bottom. During the day when she would pull herself up to standing using the coffee table or a chair, I would pat her bottom gently (to let her feel where she would be landing) and then pull her down to a sitting position. We would do this a few times as a game and soon she figured out how to get herself down. Hope this helps...