Chail, less crowdy place near shimla just 50km far, you'd love it as it won't take much time to reach here & return back to Shimla same day, next day explore shimla & then return back to Delhi. I have been here thrice, perfect for weekend trip. Go through one of my trip to Chail via bike, have a look of the destination & decide.
Here is the list of best places to visit solo in October from Delhi (FOR WEEKEND) Rishikesh, Shimla, Ladakh, Dehradun, Jaipur, Kasauli, Lansdowne, Kasol, Mussoorie, Sariska Tiger Reserve, Alwar, Kullu, Solang Valley, Agra, Nainital, Bir, Haridwar, Manali, Pushkar, Bharatpur, Spiti Valey, and many more.