I have this condition called costochondritis , does smoking weed makes it worse ?

It does: Some studies suggest that costochondritis could be caused by Marijuana, especially for people who are male. The fact is that Marijuana use may have a wide range of effects, particularly on cardiopulmonary and mental health. The muscle relaxant and physical therapy is much better for your condition.

Certainly does not: Make it better, since delayed healing is a known effect, but if that replaces other narcotics you ate taking to alleviate pain, make sure your doctor know about it and approve it.