One should be worried about a smashed finger and seek medical attention if:

• The finger is bent and cannot be straightened.
• The skin is cut open and bone is exposed.
• You are unable to move or feel the tip of the finger.
• The injury involves the palm or any of the joints, including finger joints or the wrist.
• The fingernail is not sitting properly on the nail bed.
• Severe pain that does not improve.
• Severe swelling lasting more than two days.
• The finger is misshapen, crooked, or disfigured.
• Numbness, burning, or tingling sensations occur.
• A crack was heard at the time of injury.
• Deep wounds that might require stitches.
• Symptoms get worse over time or there is loss of sensation.
• There is blood under the nail causing pressure.

For minor injuries not involving joints or nails, rest, ice, elevation, and over-the-counter pain relief may suffice. However, for any of the above signs, it is advisable to consult a healthcare professional for proper evaluation and treatment, including potential X-rays and splinting if necessary.