"I can speak a little bit of Welsh."
Translation:Dw i'n gallu siarad tipyn bach o Gymraeg.
Little difference, really - tipyn bach = tamaid bach in many situations - different ways of saying much the same thing. Tamaid is often used for a a small piece of something larger, but it is used more generally as well. There are other variations, too.
If you look at tamaid and tipyn in www.gweiadur.com you will see various examples of both being used as well as links to other, similar words and expressions.