* Professional Locksmith: This is the most reliable and often the quickest solution. A locksmith specializing in older vehicles will have the tools and expertise to open the trunk without causing damage. They can likely get into the trunk without damaging the paint or bodywork.
* Getting to the inside of the car: If you can access the interior somehow (e.g., a slightly open window, a missing or broken window), you *might* be able to reach the trunk release mechanism from inside the car. However, this depends entirely on the design of your specific vehicle and the extent of access you have.
* Emergency Trunk Release Cable (If Equipped): Some older cars *might* have had an emergency trunk release cable accessible from the passenger compartment. It's a long shot; the location would vary depending on the model year and trim level. Check your owner's manual (if you have it) or look for any cable-like mechanisms under the dash or near the rear seat. This is unlikely but worth a quick check.
* Attempting to pick the trunk lock (Not Recommended): Unless you have experience in lock picking, this is highly discouraged. You could easily damage the lock and potentially cause more problems.
In short: Call a locksmith. It's the safest and most effective way to resolve this. Trying other methods could lead to damage or further frustration. Remember to provide the locksmith with the year, make, and model of your vehicle for the best service.