I'm 6 weeks post-op, can I put an ice pack on the graft site. I have a raised bump on my head.

It is best to contact your doctor about post operative care and instructions since each doctor has a different regimen.  You should find out what the bump is before putting ice on it.

Putting ice on your head at this point will not injure anything however you should know what you are treating.This bump might be from folliculitis (infection) which might require antibiotics and/or drainage. I would recommend returning to your surgeon for evaluation.

Icing the area is perfectly safe to do at this point, although any sort of bump after a month is not normal and you should see your doctor about what might be causing it.

At 6 weeks, whever you did I doubt that it caused significant problems that can harm your grafts. Don't worry and don't do it if your instincts tell you not to do it