Hi and welcome to the Chiari forum.
Firstly the use of medical MJ is very different from the type many smoke to get high.....medical MJ does not have the amounts of THC that causes one to get high, but benefits from the high concentrations of CBD to help with all sorts of pain.
I have not tried the oils but have used a salve and intensive creams of CBD and it helps me. Mine is muscle pain due to EDS.
BUT you also need to look at what is causing your pain....to say Chiari pain, that could indicate many things, and you should try to figure out just what pain or type of pain you are trying to ease. Since traditional pain meds do not work, it is most likely neurological pain and meds do not help that......
Have you had surgery, or DX'd with any of the related conditions?
Chiari is on the approved medial MJ list in Illinois and I got my card a few months ago. I find a lot of relief from the topical balm which I use on my neck and shoulder. As Selma mentioned, it does not have THC so will not make you feel high. I also tried a CBD-only capsule which didn't work as well for me, but everyone is different.
Dispensaries also sell THC products but I only use those to relieve pain at night time (ie: not at work or while driving). Be careful with this if you are not used to THC, some products are quite potent!
I am now 4 weeks out from decompression surgery. I am also looking into mmj for the pain. I have an appointment monday at the doctors to see if i can get the card. The pain is still bad after the surgery 4 weeks out. I have been on oxycodone, gabapentin, and muscle relaxers. They help sometimes and sometimes they don't. Does your doctor say why they can't operate. My main pain was in my arms and feels like you hit your funny bone all the time and its ice cold on the inside. I was told by the neurosurgeon that he could stop the progression but any pain i had before the surgery (like the arm pain and insomnia) was a 50/50 chance of it reversing itself. This is what he has seen in the people he has done the surgery on. He is in NYC and has done hundreds of these. I am hoping time will help but also looking into the mmj because I need to get back to work in a month.