You’ll have a ton of choices for your future if you choose nursing. It can lead you down so many roads. If you can shadow please do so in a few different environments like public health and case management in addition to hospital/direct patient care. If you find it doesn’t suit you then absolutely don’t hesitate towards ultra sound.
There’s plenty of AS to BS programs out there that are online where you can complete your degree. As for biochemistry, it’s a good degree before going on to a grad/professional program after undergrad. You should also shadow a dietitian in a couple different environments as well. My friend works with adults with diabetes who mostly had/going to have bariatric surgery and loves it, it’s very hands on. My long term care facility has a dietician that works mostly from her cubicle. It really depends on what fits you the most.