not space but high altitude.http://www.youtube.com/watch?v=RpwJOhuIboU

No nuclear weapons have ever been filmed or photographed from space — at least, none where the footage has been released. During the last US atmospheric nuclear test series (1962), a lot of data was taken of nuclear explosions at high altitudes using sounding rockets, with the goal for developing satellites that could detect nuclear explosions (for Project Vela Hotel). The Vela satellites don't film anything, though, they just look for characteristic double-peak emission patterns. The one example of Vela output that we have in the public domain is of a potential nuclear test over the South Atlantic Ocean (putatively by Israel and/or South Africa), but whether it is actually a nuclear test is debated (it may be a satellite malfunction; I lean towards test, myself). Anyway, it gives you some indication of what this data looks like: not very exciting.

Were there other opportunities to film atmospheric tests? Yes. China and France continued atmospheric testing for a long while after the US/USSR/UK stopped testing in the atmosphere. Presumably the US used its satellites to track those as well. But I have never seen data derived from that, and I doubt the data in question was in a highly visual form.

(Nuclear weapons have been set off in near outer space and filmed from the ground, the opposite of what you have asked. As for what a nuclear weapon from space would look like — a bright pinprick of light that quickly dies out is probably not a bad guess.)

It should be noted that Sputnik launched in 1957 and the Partial Nuclear Test ban treaty was signed in 1963. The ban forbade all above ground nuclear test and was signed by both USA and the USSR. Thus it was only a short window for nuclear test to be filmed. The ban was shortly after the conclusion of the Mercury program so we only had 7 manned space flights at that point that could have filmed an explosion. and doing so may have detracted from the peaceful exploration that the space flights were suppose to promote.

I couldn't find anything actually filmed from space, but there was a number of tests conducted by the US in the early 60s on the effects of nuclear weapons in the upper atmosphere, of which this is one. http://en.wikipedia.org/wiki/Johnston_Atoll#National_nuclear_weapon_test_site_1958-1963