Thank you for your query.
Cocaine is one particularly dangerous recreational drug. It can cause a lot health issues form nasal irritation to heart attack.
Thinning of nasal mucosa is a known side effect of cocaine abuse. Stopping the drug is the solution for that, as you rightly said. But long term cocaine use can also lead on to nasal septal (bone in the middle of nose) perforation. So you may want to see a Doctor to make sure there is only nasal mucosa thinning, not perforation. You can examine yourself in the mirror and see for yourself. Also you have have your GP check it for you when you have a routine visit. No emergency medical helps is required.
But if you find it difficult to quit he cocaine habbit, you should get professional help.
Hope this helps.
You need to consult a Doctor for this particular problem. You body will attempt to repair the nasal mucosa. In case if you experience bleeding from the nose you can get medical help.