Welcome to the forum
"Best walk" is a bit subjective. My best walk would be to catch the bus to Ambleside and walk back over and along the fells.
Other people's "best walk" may be a Langdale Pikes round for getting up high/scrambles.
Another "best walk" might be exploring the waterfalls, caves and old mining areas around the Langdale valley.
Looking forwards already to your trip report, whatever walk you end up doing