My 2 year old son head butted me 2 days ago in the chest and now the pains are getting worse when i move around?

This sounds like a bruise to your chest muscle or ribs, which will get better over time. However, I would recommend that you be examined by your doctor and possibly get an X-ray to be sure there’s no fracture.

It would be difficult for a two year old to cause any significant injury to your chest, unlike an eye or a nose. You may however have suffered an unpleasant bruise or soft tissue injury. 2 year olds are rather indiscriminate in how hard they fling their bodies around. Try some warm compresses and paracetamol. It should get better.