You need a thorough clinical examination and sigmoidoscopy with baseline blood investigations and stool tests. Your history is suggestive of fistula or perianal abscess.
Next Steps
since you are a diabetic you should not neglect these symptoms and visit a surgeon sooner
Health Tips
regular sitz bath with maintaining local hygiene in anal area avoiding constipation and straining for stools with healthy diet and plenty of liquids orally will help you