I have a small callus like patch of skin on my lft calf, been there for over 5 yrs. Should I be worried about it? It does hurt at times

See a doctor. See a doctor. It may need to be biopsied for proper diagnosis. Need to rule out skin cancer or other skin disorder that may require treatment.
ABCD changes. Skin changes may be benign or can sometimes be cancer. An unchanging spot is less likely to be cancer. Abcd changes are concerning for possible cancer. If your spot is asymmetric, has an irregular border, color is dark or two-toned, or if the diameter is greater than 6 mm (size of a pencil eraser), you should get it checked out. If it is bothering you (itching or pain), get it checked too.