I have scoliosis, a spinal curvature. It'slight but still causes neck pain when I make certain movements for an extended length of time. Several doctors and a chiropractor have told me my neck hurts because I've strained it. It takes time for those muscles to relax and go back in place. It's taken several weeks for the pain to subside. I also get chronic headaches.
Chiropractic didn't help except the doctor was able to explain the cause for me. I've taken muscle relaxants when I can't function and those do help. Heat helps. Moist heat is a bit better. Maintaining good posture helps. Exercises or physical therapy sometimes lessen the pain. If I could strengthen my neck and shoulder muscles I would not sprain it as easily.
I can't carry heavy objects hanging down from my arm. Once I figured that out and stopped doing it I had pain less often. Sounds like this will be a one time condition for you because you won't carry baby on your back with a front pack.
Expect to have pain for several weeks. Those muscles have been stretched and it takes time for them to heal.
BTW: an x-ray or MRI will not show soft tissue damage. It will only show if your spine is damaged.