16. 1 yr neph.elbows me accidently in breast. they are sore & feel like knots are in them. could this be cancerous or just a bruise ?

Just a bruise likely: If the soreness and lump is in the part of the breast your nephew accidentally struck, it is almost certainly a bruise or even a hematoma(bleeding into breast). It should go away in a few weeks. If it doesn't go away, you should see your physician. Breast cancer if very rare but not unheard of at 16 years of age.

Breast Fat Necrosis: Sounds like what you may have is breast fat necrosis which is basically fatty tissue that has been bruised. You should follow this up with your primary doctor. Hope this helps!

Bruised: Trauma to the breast can certainly cause bruising and pain. You should discuss what happened with your mom or dad. If the pain doesnt get better with nsaids (ibuprofen) and or heat and cold let them know, so that they can let your doctor evaluate you.

Not cancer.: Trauma does not cause cancer, trauma causes bleeding, tissue injury. Try simple analgesics (acetomenophen). If there is a lump or briuse that does not go away, or pain persists, get checked by a professional.