Welcome to HCM
We understand your concerns
From the description you gave, it should not be that troublesome. As you youself concluded, the pain might be due to some sort of sprain
which happened during football training sessions. You must have used some sort of pain relief gels for soothing comfort. Internal sprains always pains in certain positions and don't in some other positions. Quite natural. Do some hot water fermenttion using olive oil application and use pain relief gels for three days. If there is no respite, then consult a physician.
Get well soon.