I'm not on hormones at this point, but I think you're going to be fine. Most people have to be on testosterone for months before they see significant changes. (I'm assuming Nebido is a brand of T?) I'm really not sure what a one-time large dose will do, but testosterone is a substance naturally made by the body, so I doubt you can actually poison yourself with it.
Hopefully, someone on here who actually takes it can give you more info. There's also always the option of calling a pharmacist and just not giving your name.