well, i already feel rather stupid talking to myself but here is what was said to my mate after he visit the dentist. hopefully, it'll help to someone passing along in the future.
anyway, it turned out that after my mate followed it for few days that his lump was changing size almost daily, sometimes growing up and becoming really hard, and then on other days becoming smaller and softer.
after he explained this to a dentist, and after the dentist had a poke around, he was told that its probably only a stone in sublingual gland since cancer doesn't move freely about and doesn't change size to smaller, only to bigger.
after that he was told that since he doesn't have any pain whatsoever that he just keeps an eye on it and come back if it starts to grow and/or hurt. needless to say my mate was rather relieved.
does this make sense? can gland enlarged from stone really be hard?