Indeed. Lack of stretching/warming up then 0-100% effort. There's no fool like an old fool!
How long before I can get back on the bike do you think? Some light spinning on the turbo perhaps?
As with any strain/sprain/tear I'd take it very easy, carefully stretching it to determine amount of pain. I've personally found stretches are better for any kind of muscle damage (aiding recovery) than actually working them further. Although it really would depend on the level of damage. I've sprained muscles before and had to continue working them, usually resulting in some bruising and a far longer extended recovery time.
Bear in mind I'm no medical professional! Just quite good at hurting myself!