I had an interview about 2 years back for the student visa for the USA from Nepal. At the time I trusted the consultancy and it gave me the I-20 telling me that I am admitted to the college and went to the embassy for the interview. There I found out that the I-20 was fake and they interrogated me and the consular officer told me not to apply again. Does that mean I am permanently banned?
I think you are very fortunate. The immigration officer ruled your application ineligible and denied your visa but they did not flag it for fraud and they did not ban you.
Ineligible is the same as denied: https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/visa-denials.html
You are free to reapply at any time however you do have to say a prior visa application was denied
Once you have a denial on your record, future applications get scrutinized much more so you should make sure your next application is faultless.
Do not trust local agencies consultancies that arrange both the school and the visa. They are often fraudulent as you have found out.