Q: What is the name of this weed I found in my lawn grass?
A: It looks like Florida Bellflower, Campanula floridana, which is native to Florida. It is a perennial wildflower which makes it more difficult to control as it propagates by rhizomes and seeds. This wildflower can root at each node making it a proficient grower.
Florida Bellflower is often found in over irrigated lawns, moist areas or poorly drained soil. It has small purple flowers bloom year round. Florida Bellflower grows up to 12 inches tall and about 6 inches wide; tolerates full sun to partial shade. Typically found in cold hardiness zones 8-10.
Best management practice is to reduce water as it cannot tolerate dry areas. Chemical management can be done by applying atrazine in October and March to control seed production. While I know you are not happy with the plant in your lawn, it might not be a bad plant for those areas near retention ponds to help reduce erosion.