Is it possible you could have nasal polyps? I had nasal polyps surgically removed a couple of years ago to regain my sense of smell, and so I could breathe through my nose again. I googled and it does look like there was some research on using Azathioprine to treat nasal polyps:https://pubmed.ncbi.nlm.nih.gov/30748107/
As any salicylate, including mesalazine tablets can cause polyps to grow it's possible that the combination of coming off Aza (which was suppressing them) and increasing Lialda (which can cause polyps to increase in size) could've exacerbated things if you do have nasal polyps.
If symptoms persist, and it's not just a one off viral infection I'd suggest you get checked by an ENT specialist to rule in / out nasal polyps. If you do have them you can try to shrink them with a nasal steroid spray, or have them removed surgically.
Post Edited (UCyousee) : 8/15/2021 3:24:44 PM (GMT-6)