Pain on left rib

Hi mummies! I’m a FTM at 23 weeks. Been trying to sleep more on my left as I’m aware it’s better for baby. (I actually prefer sleeping on my back but it’s definitely getting more challenging as my bump grows) However I’ve recently noticed that when I do sleep on my left, my left rib (below breast) tend to feel tender and sore, making it really uncomfortable to sleep on my left. Not sure if anyone has experienced this before? 😕 Will definitely check with gynae during my 24 week appt!