I used unprescribed antibiotics

I was having a cold and just took one pill of cliacil then I understood I did something terrible but it was too late. Then I went to the doctor but forgot to ask about the antibiotic I took. Should I continue to that antibiotic to not make the bacterias get powerful or just one pill won't give them resistance?

Antibiotics are useless for colds which are usually viruses therefore antibiotics are contra indicated.