What you do next depends on several factors.  Since you obseverved this for the first time today, you can wait a day or two and see if it gets better on its own UNLESS you are running a fever or the redness gets worse.  If that happens, you need to call the doctor right away in case you have an infection.  Depending on your age and medical history, there are many possible causes for breast lumps.  If this lump is worrying you, you could go ahead and make an appointment to have this one evaluated.  If you don't have easy access to medical care or if you prefer to wait, it is probably safe to wait a week or two to see if the situation resolves on its own after your period is over.  Many women have lumpy breasts that get better after each period.  Only you know your normal degree of "lumpiness" and your stress level over this new lump.  Never wait more than a month to have breast changes evaluated.  I hope that this turns out to be the kind of lumpiness that is routine for many women.  Let us know what you find out.