Worst feeling ever

I've never felt like a worse mother than when I tried the nail polish remover on my daughter's nails to get her to stop sucking her finger. I let it dry as the tip suggests but she cried that it tasted awful and she couldn't even sleep very long. It wasn't like a pouty cry she was just exhausted. I was also scared that it could have caused her harm. I decided to try it myself and it was so awful. I couldn't do it to her again. Maybe she was just too little but I was told we need to do this and that to get her to stop. I am not going to force her to stop that way. I just can't. It broke my heart.