I have a sort of bruise on my chin (it looks like little purple dots) but I didn't get hit .
It sounds like you may be experiencing petechiae, which are tiny purple, red, or brown spots on the skin. Petechiae can be caused by various factors such as straining, coughing, or even certain medications. However, it is important to rule out any underlying medical conditions that may be causing this. I recommend you consult with a healthcare professional to determine the exact cause and appropriate treatment.