EE completed putting pump PP131 online. They walked by pump and the spool piece around the intake started spraying hot slurry. Hit them on right arm and right side. EE reported injury, seen by on-site EMS, went back to work. EE went to clinic on 8/23, diagnosed with cellulitis. On 8/26 follow-up put on restrictions. Site offering modified duty. Became reportable on 8/23.