You'll have to protect the surrounding plants with plastic and spray the thistle with weed killer.
Here's a good idea for trying to avoid the herbicides if possible, because they will affect other plants once they leech into the soil. https://homeguides.sfgate.com/way-rid-thistles-garden-100512.html
Good post from Courtney.
Thistle will keep spreading if not treated, it's taproot system is very extensive. Our neighbor has a hosta border by her house and thistle took root in it, now it is in our yard. Not pretty.
I put on heavy duty leather gloves and pull while releasing the roots with a small shovel. I wiggle while I work ro get maximum root out.