Sost, as part of the Hunza Valley in Pakistan, is relatively safe as compared to other regions in the country. The local people are hospitable and women can travel around without much hassle. However, bear in mind that it is important to respect local traditions and customs. Also, the language barrier could be a challenge, but some locals do speak English. It's recommended to travel during the day and stay around populated areas to ensure safety. Like anywhere, it is essential to be aware of your surroundings, especially if you are a solo female traveler.