hi..thanks for the query.
It is unlikely that there is a persistent swelling due to an injection done wrongly.
It is likely that you have a haematoma ,but unless there is a repeated injury, this should not occur from an injection.Swelling may due to an infected cyst
.Pain,swelling, color change may be a manifestation of cellulitis in the area.
I would advise you to visit your dermatologist
or primary care
physician at least to start oral antibiotics
Hop this is helpful.