4 weeks post FUE. I played soccer and got hit on the recipient area and started bleeding. Have I damaged new follicles? (photo)

In general bleeding at the transplant site is not a good sign after having surgery. If you are concerned see your doctor for a check up.

I doubt you would have damaged your new grafts. However, please go back to your hair transplant surgeon to make sure that the injury is not deep. A thorough examination will put your mind at ease. After 7 days all the grafts are secure.

After 6 days the grafts are in solidly and not likely to be dislodged.  After 4 weeks, they are definitely safe and nothing can cause them to fall out.  You most likely just suffered an abrasion to the scalp so there is little chance that you damaged a graft.  However, a deep gash could result in scarring and potentially some damage to follicles.  I agree that a visit to you doctor should put your mind at ease.