It may be related to the pain you had in that tooth or it might not. Is
there any discharge coming out of it; either constantly or
intermittantly? The thing is, lumps like that are usually either
inflammatory or they are neoplasic. It is not really possible to say at
this point what it is. All that can be said is that it should be
examined and xray-ed soon. If you have no pain, let's hope it stays that
way during your stay and when you take the plane (change of pressure).
From where I sit the three things I would look for are periodontal
abcess (gums), periapical abcess (with draining, indicating need for a
root canal), or neoplasia (cancer). I don't think it is possible to be
more specific than that.
Hope this helps
SP