There is a chance that the solid, round, and movable object under your lower jaw in the lower part of molar teeth may be due to salivary gland stone or lymph node. But it need physical examination to determine the actual cause.

The tooth starts to ache which suggests that you may have a cavity. If you do not take care of it properly, it may go on to the neighboring teeth, thus causing the recurrence of the problem. This happens because the bacteria are attacking the affected tooth and the gum. The main thing you need to do is to avoid sweets to cut off the bacteria that are contributing to the problem. In particular, ibuprofen, an over-the-counter medicine, and sometimes a prescription, are all good options.

LIP SWELLING can be a side effect of Flexing tablets . Reduce dosage. Consult a DOCTOR if swelling persists . 

I would recommend that you get to the dentist today. A visit to the ER will only offer a temporary solution. This condition would be treated by a dentist.