I'm no doctor but I do play one on TV (just kidding).

I would have it checked out personally. I checked on the web site WebMD and this is what they said as general guidelines on bruising (also called contusions by the docs)

Consult Your Doctor If:

* You have a bruise that swells or is extremely painful, especially if you take blood-thinning medication.

* A bruise to a toe or finger results in a hemorrhage (collection of blood) under a toenail or fingernail.

* You notice that you're bruising easily or for no apparent reason.

* A bruise does not fade significantly within 10 days or fails to fade completely after three weeks.


I think the last bullet point applies to you. I may be nothing, but 4 weeks is a bit longer than usual. Probably nothing they can do for it, but it doesn't hurt to get a professional opinion. Good luck!