It doesn't look like it's possible in the app. You'd have to log in on a browser, go to your profile settings, and go to the "blocked" tab.
For what it's worth... I think the mobile browser experience is currently superior to Jerboa anyway. The scrolling is smoother and if you open posts in a new tab, you can just close the tab when you're done and you don't wind up back at the top of the feed. I have high hopes for the app but man does it drive me nuts when I try to use it.
I have another one, i want to block the entire instance lemmynsfw.com, as it is a porn instance, and i dont want it in my feed, especially at work, and they are popular enough (in relation to all the others) to come up on the main feed.
edit: i don't know how to fix your problem... i just had a hunt through the app...
This isn't a good solution. I too would like to block instances whose sole purpose is to host porn, but I don't want to hide NSFW on other instances: things get marked NSFW for language/triggers, medical gore, any number of reasons that aren't outright porn.
I'd like to hitchhike onto this because I don't know if I have an instance blocked or not. Is like to join the Ireland community which is on lemmygrad.ml but it's not showing in the search. I can't seem to centre on an answer to whether that's expected behaviour or not.
I won't create a bug as it's likely a me problem, but if anyone has ideas on what i'm doing wrong, i'd appreciate a hint.