It does sound like you may have the start of a boil. Which you can apply a hot moist compress to the area, and this will promote the lump to come to a head to burst. Don't squeeze it, always let it burst on it's own, as if you do squeeze this it can cause further infection.
If you can't get it to come to a head or burst on it's own, do follow up with your doctor, as it may need to be lanced.
As far as cancer, if it were lymph node type cancer, it generally doesn't hurt, which from location, you being overweight etc, does indicate boil. The hot compress will help, along with ibuprofen too.
Hope this helps, If you need anything else please feel free to ask. If you found this helpful don't forget to click the *ACCEPT* button and leave *POSITIVE* feedback.