I have a not like bump on my shoulder, what could it be?

Many possibilities. If it showed up abruptly and has not changes at all, it is most likely a dermatofibroma, which is a benign, stable, scar- like condition. Cysts and malignant tumors can also present this way so it really is best to schedule an appointment with a dermatologist. If he or she is not certain, a biopsy will be performed where a small sample is taken and send to the lab under local anesthesia.