Can rib pain after doing heavy weight exercise.is this a harmful condition? i'm worried?

There are a few possibilities. Most commonly is a muscle strain above or may be in the muscles that are between the ribs (intercostal muscles). These can be painful, because breathing or twisting the torso will likely hurt. It is unlikely you fractured a rib with exercise. Since sounds worrisome to you, you may want to see a doctor for a specific assessment of your pain in case is another cause.

Most likely too much weight for you. Also poor technique. If you are otherwise in good health, I would urge you to get a qualified trainer teach you the proper technique. By the way you should describe "rib pain" in greater detail including features such tenderness over a rib or the muscles between the ribs. To avoid a permanent problem, see the doctor before you lift weights again. Good luck.