When you topped the plant, did you cut at a 45 degree angle? Often, when pinching the or cutting clones off the scion, you can get an air bubble inside the top that travels down the stem. Is this "nube" part of new growth? If it's just developed on the area right below the pinch and travels down, it's likely an embolism that could serious damage to the plant. If it travels lover, cut it off immediately. If it's new growth it's your plant attempting to grow back, and will likely split into two branches that spread out. This is good and provides more internodes for a higher yield. Wait and see what direction this nube goes, then let me know what happens.