I would not recommend a pain clinic job, having worked at a pain clinic as my first NP job, it can be rewarding, especially if you can help someone reduce their pain and hopefully their dependency on opiates. I would take into account, the national "war" on opiates and by circumstance, those that prescribe them. Most states (if not all) have a database to track who is getting prescription pain killers and who is writing them, this is to stop doctor shopping and the "candy man" syndrome. Many groups and many state boards are monitoring the providers and if they get out of whack with the job that they do, they get the attention of regulators.
As a result, many PCP are stopping writing for pain pills and referring the patients to the pain clinics, thereby transferring the risk to that provider. I would also gather, that any good PCP has already offered PT, Braces, Shoulder, Knee injections, etc. Which ultimately means that many of the pain clinics clientele just want the medication, every 30 days, that's just the way it is, you can't force patients to attend PT or do injections.
The most rewarding day I had at the pain clinic, was this lady came in because she was in severe pain and her PCP was too afraid to write for pain meds, I asked what was causing the pain and she pulled up her pant leg, she has these huge areas on her leg, all of the skin was gone, I was literally looking at her muscles, tendons etc. I about freaked, "why don't you have a wound vac" etc. So I wrote her something for pain, referred her to wound care and the next time she saw me, she hugged me and thanked me for helping to save her leg, but that was one of the few good times, there is much more conflict, the tension between the provider, wanting to do something, anything besides writing for a pill, and many, many patients not wanting anything but the pill.
Ultimately, the vast majority of pain clinics are either the last resort or only resort for employment of new grads or those wanting to change fields, I learned a good deal there as my very first job, lots about pain meds, using Cymbalta for Fibro, etc But I don't missing being in the top 50 of providers in the state at one point in the number of prescriptions written, I was scheduled up to 40 patients per day, crazy.
Good luck in whatever you decide to do, and as far as being "out of scope of practice" as long as you have your license and your DEA card, the rest really isn't rocket science :-) You'll be fine, but I'd think long and hard about it before you take the plunge, and if you like it, awesome, good luck!