Lump in mouth I've had for about 4 years

I have a small painless (except when I rub, poke, or prod at it) lump on the floor of my mouth right at the base of where my front bottom teeth gums meet the floor (mandibular area). It is internal, meaning you can't see it when looking in the mouth, it is under the lining of the mouth. When I first noticed it I told my dental hygenist who felt around for it but couldn't feel it - she kind of blew it off. So I too ignored it since. Now a few years later I'm wondering about it again. I told my dentist about it last week and she felt around for it but could not feel it - she basically told me not to worry about it either. It is definitely there - I can feel it with my tongue and my finger and I can kind of move it around with my finger. I also visited my doctor last week and I didn't even bother telling him thinking he wouldn't be able to feel it and would tell me not to worry. I'm wondering if I should see someone more specific to this type of problem? An oral surgeon or ENT perhaps?