What Causes Milky Discharge From Nipple After Squeezing?

im 26 yrs old..and i gently squeezed my right nipple and a tiny bit of clear/milky discharge came out. i am not pregnant and have never been before, i squeezed my left nipple and nothing came out so it is just the one nipple.i hav irregular periods..is it serious problems nd needs any medication? i dont know what s happening, can anyone help?