Yes Please. I Have To Use A Sling To Hold

Yes please. I have to use a sling to hold up my arms after an op to repair the torn tendons. After using sling for 4 weeks it is chaffing my skin which is coming out in a rash. It is not itching and antihistamine cream does not reduce rash which has also developed tiny boils. Purely an abrasion reaction specially as wearing skin at night as well.cannot drive yet so cannot go to doctor. What can I get from chemist to reduce rash?
Thanks
Regards