Oh I am so sorry - I was very prone to this all through breastfeeding, and it is screamingly painful. I really sympathise.
I tried everything I could and always got it moving in the end without mastitis - although the longest was nearly two days which was a killer.
Have a nice hot bath with Epsom Salts.
Keep very firmly massaging the breast tissue where the blockage is - A LOT. Just lie there and massage and massage and massage. My DH did it for me sometimes, when I was too sore to do it to myself.
Almost unbearably hot flannels on the breast, then more massage.
Get the baby to feed upside down from the normal way. I tried all different positions, including on all fours over her, rugby ball and with her over my shoulder drinking upside down.
Try hand expressing - that cleared it for me one time.
Massage with your hand making a C shape.
Breastpumping.
Kneading using your knuckles.
Castor oil compress.
Electric toothbrush on the area - not the brush part, just some part of it that vibrates.
Hope this helps.