It would be a good idea to keep an eye on that, as it could be leading to mastitis. Usually dropping one feed at a time is a good way to avoid mastitis, but sometimes when they are younger (especially under 12 months) that is still not slowly enough to avoid mastitis. It might be an idea to give DD an extra small feed today, or to express some milk from that side, and see how you go from there. If it doesn't get better then it is a good idea to keep draining milk. If you start to feel feverish, see red on your breast of feel really fluey, please go and see a GP for some antibiotics. GL!