I'm 23 and one of my boobs is always sore i've had a child she is 2?

Still breast feeding: The answer as usual depends. Are you still breast feeding? If so, a blocked duct is still a likely cause. Hormone changes like pregnancy or stress are frequent. From your question it seems as though it is a long term issue and not likely to be an acute process like an infection. Are there color changes, tenseness. Does it hurt at all times or only a particular time. Much to know and learn.

Need to examine: It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. You may take acetaminophen, not more than 4 gm in one day, no alcohol. If that does not help or it gets worse you ought see a doctor.