Advice regarding Alopecia areata

Hi guys so recently one randomly morning i noticed that a patch of hair is missing from my head and it has a very neat smooth bald spot there, this happened overnight. I don't have hairfall issues or anything and it happened towards the front side of head and not towards the usual bald spot area. So on searching i found out that it's called alopecia areata and it usually happens because your immune system mistakenly attacks hair follicles leading to spot like these. Luckily i just have this one spot and it's perfectly covered because i have a hairstyle which covers it. I visited a dermatologist today and they wrote a injection for it which will be taken on head on the spot and also wrote a lotion to be applied on the spot every night. Has anyone or their known one faced this condition, on the internet it says there's no cure for this and the hair grows back automatically after a while. I will be applying the lotion on the spot but i am not so sure about the injection so if anyone can guide me about it, if it's necessary or not because one of my friends said injection and all are useless for this, just give it time