Well, any change in position takes "getting used to."
Are you spending a lot of time "in the drops?" If so, don't. Reserve the drop position for special times, such as against the wind to fast downhills, if you like.
Also, learn to "tuck" your chin into your chest, rather than stretching your neck out.
I would give it a few more tries, easing into it. If the issue doesn't resolve, look at having your bars raised a bit. Most of us have had to do that (I am almost 68 yo) to accommodate our "changing" body. But, I still like drop bars.
Also, if you are using a visor, it will cause neck stretch.