What Causes Ceased Upward Growth In Toe Nails?

Hi. one of my toenail suddenly with no apparent reason stopped growing upwards. First I noticed a little bit of pain around base of nail (only when I touch it) and its a little bit thicker area around base of nail under the skin compared to another big toenail. Also I can t even see cuticle on that nail anymore. Nail itself looks fine, not yellow, not crumbly, corners are not ingrown, I didnt injure it before. So it s a complete mystery to me what s going on. Would appreciate advise. Thank you