Most likely a rubbing disc brake unless the wheel is damaged and tyre rubbing on the frame?
Anymore information so that we can help you further.
Start with undoing you calliper at the frame (the two hex bolts) just so they wobble a bit. Next spin the wheel then apply the brakes. Keeping the brake applied with one hand carefully tighten up the bolts to the recommended torque (usually about 5N, which is about just over finger tight if you haven’t a torque wrench)