Injections

I am after some advice and wondered if any of you had been through a similar situation. My 12 year old son has an ingrowing toe nail which has got really bad and needs operating on. The NHS appointment was going to be at least 4 months away so we tried the Foot Clinic. He, understandably, had a complete melt down and it was impossible to give him the local anaesthetic injection and had to give up. He is not reassured by getting some ointment to numb the area. He HAS to have the operation. Any advice?