A hard bump on the arm, you need to carefully observe whether the bump has obvious pain, if there is a significant bump with hand touch, accompanied by pressure pain, consider the possibility of inflammatory nodules caused after excitation in folliculitis, will gradually recover over time, if you want to accelerate the repair, it is advisable to apply mupirocin cream or fusidic acid ointment, which can effectively promote local blood circulation up, to The role of anti-inflammatory. If the hard bumps are not painful and fixed and do not move, consider the possibility that they are bone warts and need to be dealt with by an orthopedic surgeon. If the bumps have some elasticity and you can feel the movement with hand pressure, you need to choose dermatological surgery to remove them and do pathological examination to confirm the diagnosis.