43 male uncircumcised. i suspect i may have bxo due to foreskin getting lighter in color and a little tighter and some white areas. noticeable when foreskin is pulled back. who should i see a dermatologist or urologist? could this also be cancer?

A little knowledge is a dangerous thing. Yes do go and see a dermatologist or a urologist, and make sure that they understand why you are coming. This article may help answer your questions: https://www.cuh.nhs.uk/patient-information/balanitis-xerotica-obliterans-bxo-in-boys-information-for-parents-and-carers/#:~:text=What%20is%20BXO%3F,bladder%20out%20of%20the%20body).

From your description not cancer. You can see either of the specialists