Irreversible pupitis is a very painful condition in both children and adults. In children it can come on quite quickly as dental caries progresses rapidly through deciduous (baby) teeth.
Irreversible pulpitis in baby teeth is treated by either removing some or all of the nerve of the tooth or by taking out the tooth completely.
Irreversible pulpitis may be managed with pain killers and hygiene measures however if it gets more severe then it is likely to need professional attention. It can also become an abscess and cause swelling. Any uncontrolled swelling especially when heading towards the neck and throat needs to be URGENTLY treated at an A&E department.
Your tooth will DEFINITELY need treatment from a dentist. The dentist will decide whether the tooth can be saved through a treatment option called pulpotomy or pulpectomy, otherwise they may recommend extraction of the tooth.