Skin colour differences treatment

Hi, I’ve never done aesthetic treatment before and is unsure about derma/facial spa/aesthetic clinics
But I’m not sure what has cause my face skin tone to be much darker than the rest of my body and hands. The irony is my face is the only place I always put sunscreen and foundation. I also consistently use facial oil to rinse my face. Wondering if this could be solved with skin treatment? Could be sun damage or maybe used too much retinol etc. please help any expert on aesthetic treatments :>