Why do some wounds turn purple?

That's the bruising - if you get hit hard, the skin will turn purple - don't worry about it, it'll go down in a bit. You can always take some paracetamol to help the pain, and if it swells up lots, you can see a doctor!

It is the outcome of broken blood vessels and inflammation. In fact, this process will always take place in the initial phase of a scar. The skin area that is damaged will signal out signs to our bodies to send in blood flow to assist in the healing process.

it could possible be internal bleeding or the blood is clotted in that particular area, for more accurate description check out other websites and if it's severe visit a doc

Depending on the depth of the initial cut and how old the scar is, as well as skin type (thick, thin, elastic... etc) and how your body heals itself, the colour and texture of scars can vary.

Some wounds turn people so that we can address this wound we have. Purple and red on our bodies signals for our body and our mind that this area needs to heal, and we can be more aware of this need for healing from the color. As time passes, and as we do more healing internally and externally, the color of the wound will change. Physical wounds may change colors in a shorter amount of time than deeper emotional wounds; a cut on your arm physically will heal sooner than the equivalent to a bullet wound emotionally, therefore more attention is needed.