It's always worth learning something new! Just be aware that the music you will be capable of playing, as a beginning student, will probably have little to do with the more advanced music you will be interested in composing. Since you can already read music and have good dexterity and musicality from playing wind instruments, you may learn a little faster than other beginning students, but probably only a little. This will be a long-term learning project. On the other hand, even in the very beginning, having taken some lessons will give you better access to good violinists, and you can ask them for their honest opinion of your scores, and will be better able to understand their comments. And they are more likely to give you careful, detailed feedback if they know you are taking lessons and are serious about composing for strings. Wanting to do this is a good learning opportunity, but it's also a mark of your dedication to composing. You are taking the time to think about where there are gaps in your musical knowledge and trying to fill them. That's definitely a good mindset for a composer. (: