A red itchy rash on the inner side of my leg near the groin area for over 1 month. it decreases when i take anti biotics. i want a permanent solution?

Which antibiotics?: Tried anything yet? Can try clotrimazole, miconazole, or ketoconazole cream. Might add hydrocortisone cream for a few days. Continue azole cream for several weeks. Most groin rashes get WORSE with antibiotics. The DETAILS matter.

Erythrasma: I assume you used actual antibiotics and not antifungals . You could have Erythrasma which is a bacterial infection that just like fungus affects areas of moist skin. The rash may have well defined borders and may become brownish. Topical and sometimes oral antibiotics are necessary. Keeping the area dry is the way to prevent this. Check that you are in good health for example no diabetes