I’ve had two back spasms in the past year about 6 months apart. The first one was really bad and followed a small tweak like what you experienced. The small tweak was painful but not bad. But later that night as I was walking across my apartment, and suddenly it spasmed hard and I was locked up with all my muscles tensed for about 30 minutes before they finally released. It was really scary and I could barely breath because the muscles were so tense.
Naturally, I saw my doctor about it and he told me to use a heating pad on and off for 10 minutes at a time and to pay attention to posture. This definitely helped ease the muscles, but recovery took about 10 days. Once the pain had subsided some, he gave me the clearance to ride the bike at lower intensities. I did Z2 for about a week and then ramped up the week after at a slow and deliberate pace to gauge how I was feeling. Luckily I had no other issues as I did this. I also did all of my rides indoors at that time as a safety precaution.
The second time was a couple months ago. It was nowhere near as bad in pain or in debilitation. I skipped workouts for about 3-4 days before getting back on the bike. Just like last time, I started with Z2 and worked up to more intense workouts to gauge my body’s response and feelings. I scaled much more quickly that time as it wasn’t as intense and experience. I’ve been good since and used the heating pad to smooth things out as well.
That was my experience, and I 100% recommend going to the doctor. I presume their office can refer you to somebody while they are on vacation. It was worth it for me and gave me peace of mind. If I were in your shoes, I would not race as I’d feel as though I were jeopardizing the whole peloton if it were to spasm in the race.