Having Big Bump In Throat. Looks Open Wound. Involved In Oral Sex. Heavy Smoker. Suggest

Hi there, I have a big lump in my throat , which I originally thought was a large ulcer . I took a closer look a few days later; it is an open wound, like an ulcer, but the open bit is all black. The ulcer is sore, and has been there for about 4 days. I have recently been involved in oral sex , could that be what caused this, and should I be going to a doctor? I am also a heavy smoker, which obviously doesn't help anything, but could that be directly linked to this? Any ideas? Thank you