What are possible causes of sudden pain of top of foot with the apeearance of a bump and swelling? thank u

Cyst of some type: Several things can cause it, there are deposits like lipomas, epidermal cysts, that are benign but can be painful. A common problem in that area can be a ganglion cyst. These are small benign growths that occur on tendons. They are all easily sorted out on physical exam. You should see a primary care doctor.

Several things: Anything from fracture, or hematoma. Should be seen by your family physician and may require an x-ray if there was any significant trauma.