You are suffering from stye
in your eye with inflammatory changes in the affected lid. You will need to give hot fomentation 3-4 times day to the affected eye and use anti-biotic eye drops 3-4 times a day. Also, use anti-biotic ointment at night time.
You can continue using bactrim
tablets BD along with some anti-inflammatory tablets. If there is some pus point formation, you will have to get the affected eye lash epilated to drain the stye and bandage the eye for 24 hours at least.
This should cure the condition in 2-3 days.