Hello There,
If there is only one Blister on your toe and you do not notice same type of blister on other body part then its not a Chickenpox. You do not have accompanying symptoms like Fever, headache and loss of appetite. And you have already suffered by Chickenpox at your age of 15 then it is not a Chickenpox. Because once you suffered by Chickenpox; body develops immunity against it for the lifetime and there are rare chances to suffer by Chickenpox again in a lifetime.
Next Steps
Visit to Physician for examination of Blister and it's cure.