Hi there!
Well, without a detailed clinical evaluation it would be difficult to comment specifically on the situation, though masturbation is unlikely to be responsible for the sensory deficit; which may be related to psychological causes, vascular issues, infections/ inflammations, primary skin conditions etc. I would suggest getting this evaluated by a primary care physician initially and depending on the cause diagnosed/ suspected, it can be managed accordingly or specialist care may be sought.
Hope this is helpful.
Take care!