Redness around meatus for a long duration may be inflammatory or otherwise. Inflammatory lesions like balanitis or urethritis may bother especially in diabetics though these would invariably have urinary or inflammatory signs associated. You need to have your glycosylated haemoglobin (blood test) done to see the control of diabetes. The non-inflammatory lesion like Bowens disease or erythroplasia could be worrisome and may require biopsy for confirmation. You need to see a urologist or a dermatologist for opinion and needful.