How uncomfortable that must be I also suggest expressing from that side before expressing - express until you get a let down. It might also help to do a one-off full expression from that breast - there might some blood and lymphatic fluid there too which is stopping the milk draining well. In this case a one-off express can be very helpful. Once you've done that see how you go. If that side gets engorged again, you could try doing 2 feeds from the right side for every left side feed, to try and reduce the supply on the left side (the more you feed from a breast the more milk it makes). If you try this, it's important you express for comfort from the left side though. Whenever your breast is full enough to be hard and lumpy you are at risk of mastitis, so you need to express enough to feel comfortable again.

Best of luck hun. I hope it settles down quickly for you.