Hi,
A nipple discharge is significant and needs to be investigated further if it is persistent, comes out without squeezing the breasts, is bloody or foul smelling and is associated with a lump, nipple or skin changes etc. If the discharge happens only when you squeeze your nipples, all you have to do is to stop doing that, so the discharge will also stop. If things don’t improve, it would be best to consult your doctor in case you have an infection in your left nipple that should be treated with Antibiotics.
Take care...