I think it's a badly fixed tape rather than a bubble/blister in the plasterboard,,, it's too even all the way up
To be honest, if that's a newly built house, then the workmanship is appaling if that tape is anything to go by.
To fix it, you'll need to remove the old tape/s and re-tape. As Richard says, there might be a bit of work involved in doing that , especially if there are more of the same.
If it was me, i'd get the builder back and show him the faults, and ask him to repair them.,,, that's if he'll come back,,,, very shoddy.