Hi, Welcome to HCM, You are diabetic,and if they get any injury in there legs they are more prone to develop infection,but just do not take antibiotics without consulting Physician,yes you should inform doctor that you have allergy to penicillin,he/she will take care. Please continue your anti diabetic medicine have good control of blood sugar. If your injury is showing signs of infection you may require antibiotic and analgesic and anti inflammatory drugs. If there is any open wound proper cleaning and dressing may also be required,as also any tetanus vaccination your treating doctor will know best. It is not the question of money,please take care of yourself as treatment at proper time is very important. In the mean time keep limb elevated and take rest. I wish you recovers soon. Best of luck.