I'd have a good think about which bass to buy; I've had one or two which have hurt my neck-hand, including a Warwick 5-string which I wanted to like.
You could try different ones and also gauges of strings and I'd also suggest a low action, because there is no value in having to exert excessive force just to get the string to touch the fret.
A Status Graphite 5-string Energy with Status strings is the easiest to play bass I have and it is not one of their eye-wateringly expensive ones.
I'd also suggest, which kind of lines up with other comments, that you need to learn to recognise when discomfort/pain is your body whinging at you versus when it's telling you you're doing something wrong; I have this with my karate training, where my knees especially are shot - I can't do 100 repetitions of a kick, so I do a few and then listen to the feedback (mind you, I am 57, so the fact I can do a head kick at all isn't a bad thing).
You can take that concept with you when you try out some basses too; you don't have to buy the very first one.
I'll take a look at the Status.
The fact is that I am very well tuned in to what my body is telling me, which is why I am heading down this path. I've been playing guitar for the most part of 21 years and I know what my arms, shoulders, back, hands, and fingers are capable of right now, and it isn't good enough for me to enjoy playing. I'd rather build up strength and stamina through artificial exercises without playing a bass, without even owning one right now, than stare at a rig in the corner that I cannot play as much as I would want to and be disappointed and frustrated while I do hand exercises.
As far as potential basses, I love the Ibanez SR line. I've had some SR 300s, but my holy grail was an SR1200E, headstock seen in my little avatar pic above. Very comfortable to me, string spacing, neck, nut width, etc., all worked for me. But I had a major problem with the SR1200. The on-board eq and pre-amp was just too complicated and "moody" for me to work out. I really couldn't get it dialed in to sound like I wanted it to, and it was very frustrating to me. Looking back, I should have taken to my guitar tech and had him disable all of it and just left the pickups and tone knobs working. I would have enjoyed it much better. Because of that, I will probably just look for a good J bass when I feel I am ready to buy. The J necks and nut width are similar to the SR and work well for me. Probably going to shoot for a good deal on a used J bass, probably a CV or a VM. I don't see any reason to buy any more for a long time.