Infected gum after tooth extraction with ulcers?

Dry socket???: May depend upon the tooth that was extracted and if there was infection there prior to having it taken out. Time frame is also important- was it taken out recently or a few days have gone by? Call the dentist/oral surgeon

Tooth extraction: impossible to answer without a visual examnation and additional information. Make an appointment to have it examined by your dentist or the surgeon to did the extraction. Also, make sure you follow the post-op instructions and keep all follow-up appointments.