You are an active skateboarder and have had a fall on an outstretched hand. It has already been 3 to 4 weeks. Hematomas do take time to resolve, gradually change colour from blue black to brown and then gradually fade. Still, it would be wise if you see an orthopedician to rule out any crack fracture
, or muscle tears as you have supported yourself on a rock. If this is the case, you would need rest for the hand with cast, etc which will be decided by the orthopedician.
As it is the hand we are talking about, we cant afford to ignore it. Kindly see the orthopedician and get it checked up for your speedy recovery. Take care.