lumps

I was feeling my boobs after I watched a buzz feed video on breast examination because I've never had one or done one to myself and I felt a kind of lump on the very outside of my boob towards my underarm and it was painful.. I can't get to a doctor to see what it was until next week or so and I was wondering if anyone has had the same thing and can tell me what there's was (it felt about 3cm in diameter and was very painful)