I was scraping a porch with my mom today. I didn't think anything of it till we were going to purchase the new paint. After reading the warning about lead dust I began to worry. My mom said they had just painted the same porch about 5 years ago. Should I be concerned?

Concerned about what? A porch is outdoors, so there was probably sufficient ventilation. You probably should have worn masks, but it would take a lot of dust to have a long term affect.

So I should worry about being affected about the short exposure? Just be more cautious next time?

No you shouldn't worry, but yes be more cautious.