Achtually, most Uranium is uranium-238, which is mostly stable. People use it in glass and decorations and it causes them to glow in blacklight. It's safe as long as you aren't in daily constant contact with it or eat it.
Uranium-235 is less stable, but makes up less than 1% of Uranium on Earth. The quantity in natural uranium isn't much riskier unless you're exposed to enriched uranium which has more Uranium-235.
The byproducts of a chain reaction of U-235 fission are what cause most of the dangerous radiation. Which is to say, the leftovers of a nuclear explosion are very radioactive and dangerous, but natural uranium before exploding is mostly safe and it won't explode unless you enrich it and set up the correct conditions.
Hiroshima, Nagasaki, Chernobyl