Hello dear, yours symptoms are indicating towards formation of mucocele i.e blocking of salivary duct's opening. You can check for the mucocele pics on google and relate to yours.
Dr Bakshinder singh lyall
MDS PEDODONTICS
DR LYALL'S DENTAL CLINIC & IMPLANT CENTRE
SCO 50, Phase 11, Main Market, Mohali, Punjab
Next Steps
check by applying limited pressure around it and see if it pops out and discharge transparent fluid as it will release the pressure and might can dislodge the obstruction. apply hexagel on and over it afterwards. this remedy I am telling in case you don't have a dentist near by . if yes then do visit him without doing anything by yourself asap