Your attorney cannot legally force you to accept a settlement offer or to go to trial. S/he must act as your advocate and respect your wishes, and s/he is bound by the attorney's professional code of ethics to report all offers of settlement to you. If you are hesitant to accept such a settlement offer, be sure you talk it over thoroughly with your attorney first.
Your attorney is trained to evaluate the specific type of case you have, and s/he has a legal duty to act in your best interests. If s/he wants to settle, you need to understand why. Trials can be time consuming and expensive and there is no guarantee that you will win in the end. Further, even if you do win, in some cases (like if the insurance has already offered the maximum payout under the policy limits), it may be hard for you to collect a judgment since the insurer isn't going to pay anything above what they must under their policy agreement. Your attorney may know details about the evidence, the insurance agreement or the law in your state that could be driving the settlement offer and/or making trial inadvisable.
On the other hand, if your attorney recommends a trial, you need to listen to exactly why the attorney thinks a trial is the best strategy. Focus on the facts and reasons. Your emotions are bound to be strong, especially if you feel like you need the money from a settlement right away. However, your emotions can mislead you or convince you to agree to something that, in the long run, really is not in your best interests. Once you settle, you can't change your mind and sue later, so you should weigh carefully the proposed benefits or advantages of going to trial that your attorney may share with you.
If you still disagree with what your attorney has suggested after listening to him or her with an open mind, there is nothing wrong with getting a second opinion. However, you should generally tell the first attorney you are doing that. If you decide to hire a second attorney, you may dismiss the first one. However, you need to remember that without the contingency "payoff," you may have to pay all costs and fees that you have incurred by working with your attorney up to that point. You'll need to check your fee agreement to find out exactly what your obligations are.