As per history ..present swelling is non mobile. Correlating it with ct scan finding ..it is more likely diagnosis towards organized intramuscular haemotoma. Usually haemotoma decreases with time. But if the swelling doesn't decrease, it becomes fluctuant and mobile ..it means changes to pus/abscess/collection. For pus it needs antibiotics and drainage.
Next Steps
Get a physical checkup done to know whether it becomes pus/abscess as treatment for that is likely urgent
Health Tips
notice for any fever episode