I have a sling on because i broke my clavicle but it makes my ear go numb. this happened before when i was wearing a sax neck strap. is it a problem?

Too tight: It sounds like your strap does not fit properly. Padding under it can help. Talk to the person who supplied it about proper fit. If that does not help, talk to the doc who is treating you about it. The damage from a poor fit, if the sling is in place to long can be permanent. So get this problem addressed. Loosen it a little till then, till numbness resolves.