Warm water bath, not too hot tho! It should help loosen the shed so you can help him with a pair of tweezers. Just make sure you don’t pull if there’s too much resistance. Alternatively making a humidity chamber should help. Warm damp paper towel in a plastic container, with a lid for 20 minutes.

Want to stress, I am not an expert! I love lizards though so I suggest looking up the best supplies to use