IV precipitation

Please tell me what I did wrong. Patient was on levaquin IV. Doctor prescribed a now order for Lasix IV push. So, I stopped the levaquin, ran the Saline line at 100 for 25-30. Then I proceeded to push the lasix. I drewback and the syringe looked a little cloudy - but, because I never saw a med precipitate (I thought it crystalized immediately). I made a stupid, stupid judgement and thought it was ok. I started to push it but then second guessed myself and stopped. I turned off the pump immediately and took the line off the patient. Only then did I see the crystalization. Can you please tell me what I actually did wrong? Did I need to flush it longer or should I have gotten a new saline bag and pushed it through a new line. Luckily, the IV therapist was in the next room so, I had her look at patient's iv site, she was able to flush 10cc. I am really upset about this - I keep thinking what if i would have continued to push the lasix. What would happen? Also, I worry that some of the contaminated fluid entered the patient. Most likely not, but, would the IV flush if the precipitated fluid went into the vein? I am a new nurse, but it doesn't excuse my mistake. thanks for your response.