It is perfectly normal and no cause for alarm. If you have a close relationship you may want to offer some advice (lubrication etc) so he doesnt hurt himself
It is ok! He is at that age, my son is 10 and he has been spending a lot of time in the bathroom and hubby just had a talk with him. Just let him know not to be embarrassed, and make sure he does it in the privacy of the bathroom.
It's fine. Let him do it. Don't ever criticize or punish him as you will create much greater problems for him later in life. The one thing you can do is explain to him that it needs to be done in private...make sure it is in the bathroom or his room.