Can this be a cavity, I am not sure ?

I spotted about two weeks ago a tiny tiny speckle which to me looked like a cavity, I saw two one on each bottom side. Now I took those little mirrors dentist have and looked up top on the right side I do see a thin slightly dark line under a tooth, can that also be a cavity? I thought they were always holes or cracks. I do not have any pain either there or where I see the tiny speckle like hole. I won't be able to get an appointment until 2 weeks from now with my dad (who is a dentist in NJ) I am in Texas and will be heading there next week. So, any thoughts if that can be a cavity as well?