You probably won't need a teacher for as long as you needed one when you were learning cello. However, you do need someone to at least confirm that you are holding your instrument correctly and help you transition to finger patterns appropriate for the violin, since they are not the same as the finger patterns used on the cello. You might then need to go back to a teacher when it is time for shifting and vibrato. Bare minimum, you probably want a few months of lessons now and a few months here and there down the road if you get stuck. Bottom line, don't over-estimate your cello experience. The more you do, the more you will need someone to help you fix bad habits.