Hi Ana. You'll definitely find some good tips in this thread already. Again, for me, the most important thing is to turn the 'feeling' of wanting to write into a process, and then the process into a habit. Start writing lyrics with minimal regard for quality. Set yourself a deadline (doesn't really matter how long, just stick to it!) and have a complete lyric done in that time - doesn't matter if you think it's good or not, it must just be complete in terms of having a distinct beginning, middle and end.
You may find that you do this a number of times before you start developing material that you think is any good. You may also go back later and reuse things from earlier attempts. What matters most is that you turn feeling into process, and process into habit. This requires persistence and self-discipline.
Perhaps you might also want to find other like-minded people, and keep each other accountable in terms of those deadlines, and maybe do a lyric swap each time, to look over each other's work, critique, and maybe even contribute your own ideas.
And, far from stunting your creativity, I find it actually helps defeat all the things that get in the way (self-doubt, laziness, lack of commitment, lack of focus), and ultimately gives your creativity the most opportunity to flourish.