Real answer: you would have to be soldering for hours every day for months to be exposed to more lead than can be cleared naturally. Full-time component assembly workers do get that much exposure, so they need to take precautions to avoid poisoning. For hobbyists, you would have to eat quite a bit of solder at once before you would develop any poisoning symptoms.

edit: so, it's the frequent repeated exposure to lead (i.e. in paint and as a sugar added to wine[0]) which is harmful, not any single individual (non-acute) exposure.

[0]: https://en.wikipedia.org/wiki/Lead(II)_acetate#Sweetener