By the description given,it appears that the infection has invaded the pulp of the tooth. In such cases,there are two options,get root canal done which is usually followed by a crown(cap) or extraction of the offending tooth followed by a space maintainer. However,wherever possible root canal treatment is a more favorable option as a natural tooth is the best space maintainer for permanent teeth.

You might be wondering why your child needs a root canal.Children typically shed their baby teeth for adult teeth around 6-12 years old, but this is a big age spread and infection may precede to permanent tooth buds.In some cases your child’s root pulp may be exposed, and this can be very painful. By treating this with a root canal you can provide your child with a solution to the pain and discomfort, while restoring their tooth to its natural appearance.

Hi Uday, as per the brief history provided it seems like a pulp tissue involvement of dental decay which requires a root canal treatment. It is important to retain deciduous teeth (milk teeth) in your 5 year old as they maintain adequate space for the future permanent teeth and also local pus accumulation may discolor the permanent tooth lying below the roots of the deciduous tooth within the bone. If pain is due to pulpal involvement (which I cannot confirm without a clinical and radiological examination) please go ahead with the treatment.

Yes rct is important if pain is there. As the age of patient is 5 years she has mixed dentition stage. So rct is important to get rid of pain if infection has reached to nerve.