It's possible that your Samoyed has a torn ACL, but it's important to wait for a veterinary diagnosis to confirm. Lameness and reluctance to play or move around can be symptoms of a variety of issues, including arthritis, hip dysplasia, or a soft tissue injury.
In the meantime, it's best to limit your dog's activity and avoid activities that may exacerbate the injury. Providing a comfortable, padded place for your dog to rest can also help. You can also try applying a cold compress to the affected area to help reduce inflammation and pain.
Once your vet has diagnosed the issue, they can provide you with the appropriate treatment plan, which may include rest, pain medication, physical therapy, or surgery depending on the severity of the injury. In the meantime, it's important to monitor your dog's behavior and keep them comfortable.