(dot)ws domain

My targeted niche is reflux/heartburn/indigestion etc

I got offered a one word related domain with the .WS extension.

Is a .ws even worth it?

Theoretically there's no difference between TLDs, although a lot of people claim difficulties in ranking some TLDs. A lot of people also claim lower CTRs on the serps from non-com/net/org domains. Personally I would buy it if it's not too expensive, just for the sake of having a good one word domain in a bankable niche - you can always flip it later.