From the description which you have given , there are a few possibilities.
1. A collection in that region.
2. Development of a hernia
in that area.
I would suggest the following
1. A visit to a surgeon to evaluate the region clinically.
2. A ultrasound
examination of the abdomen.
3. Complete blood count
to look for infection.
Depending upon the results of the above evaluations , a diagnosis and proper treatment can be chalked out.