Final answer:
The nurse should immediately assess intraocular pressure to determine if the client is experiencing acute angle-closure glaucoma.
Step-by-step explanation:
The nurse should take the following action immediately: assess intraocular pressure.
Severe eye pain and nausea after cataract extraction may indicate a complication called acute angle-closure glaucoma. This occurs when there is a sudden increase in intraocular pressure due to changes in the eye's anatomy. Assessing the intraocular pressure can help determine if this is the case and prompt appropriate interventions.
An analgesic may be administered to help with pain, but assessing the intraocular pressure takes priority as it guides further management.