So i was bitten by something on my back and at the moment i have a rash and its itch but also painful. i was wondering what i can use for that ?

Insect bite: For an insect bite as you described, you can use ice on the area for 20 minutes about every 1 to 2 hours. You can also apply over-the-counter hydrocortisone cream twice daily. You should also observe the area of the bite to make sure it is not growing, or becoming more red or even a dark or black color. If you notice this, you should see your doctor for further evaluation.

Bite: Would recommend doing an anti-histamine and an anti-inflammatory like ibuprofen, this should help decrease the itching and pain. If the redness is worsening or you start noticing a discharge or in general is getting worse, should get it examined for futher treatment.