Should I be worried about this mole on my butt checks? (photos)

Thank you for your question. It's difficult to evaluate your lesion through photographs and to give a diagnosis. In my opinion, any changing or worrisome lesions on the skin should be evaluated by a dermatologist, who can look at the growths with an instrument called a dermatoscope. This scope allows the physician to look at the lesion under higher magnification for any abnormalities, and if any irregularities are present, then a biopsy should be performed. I highly recommend you consult with a board certified dermatologist to evaluate have your lesion evaluated. Take care and good luck.