TeenHealthFX is glad you are getting to know your body and are aware of it's changes!
This lump you are describing sounds like it hurts and may have scared you. Since this lump is hard and painful, you need to speak to your doctor about it. Although you are probably getting ready to start puberty and what you are feeling is likely a "breast bud" or the first stage of normal breast growth, any lump or soreness associated with your breasts at any time in your life should be taken seriously. Because of your age and the beginning of your breast development, only a doctor's exam would be able to identify if this is normal. Speak to your parents or school nurse and see a doctor.
As to when you will get your period - The average age for females to start their period is 12 1/2 years old, but some women get their periods as young as 10 or as old as 16. In general, females get their first period about 2 years after they develop breast buds. The lump in your breast may or may not be connected to you beginning puberty. When you go to the doctor for your lump, speak to him/her about this too. Getting to know your doctor and your body is part of getting older and being in charge of your health.