Try this first
Keep your dose and target yield the same. Try a slightly finer grind, then taste again.
Why this can help
Sourness can reflect a less developed extraction, but the coffee itself may also have bright acidity. Taste and adjust rather than chasing a single number.
What to try next
If the shot still tastes thin, check that the coffee is fresh and the puck is prepared evenly.
Related skills: Espresso and dialing in. Explore the Home Barista Roadmap for more context.
Every coffee and setup behaves a little differently. Make one change, taste, and keep the result that works for you.